Itunes freezes when syncing songs (-69)

Whenever I go to synch my 16GB iPod Classic, it keeps freezing on certain songs and tells me there has been an unknown error (-69). However these songs have played fine on both my iTunes and my iPod before, so they shouldn't be corrupt. Even tracks I've brought from the Store have this problem as well as those i've imported on CD. I've followed Apples Support page suggestions but I'm still having problems.

Any suggestions?

I should note that all my music is stored on an external hard drive including my iTunes folder.